Commercially-available durable, abrasion-resistant surface coatings are oftentimes manufactured from formulations which typically contain a number of ingredients, including epoxy-containing components or ingredients.
Epoxy-based surface coatings are, moreover, oftentimes typically produced from so-called "two-part" systems. For example, to produce a particular surface coating at the time of desired use, an epoxy-containing composition is combined with a hardener composition therefor. Such two-part systems are disclosed, for example, in U.S. Pat. Nos. 3,066,112 and 3,179,623, both to Bowen, and U.S. Pat. No. 3,822,229 to McMaster.
More particularly, in a two-part coating system of this sort, the epoxy-containing composition can be--and oftentimes is--hardened with an amine-containing composition, as is well known in the art. Systems of this sort are disclosed, for example, in U.S. Pat. No. 4,399,242 to Fowler et al., U.S. Pat. No. 4,557,870 to Rodgers et al., U.S. Pat. No. 4,588,617 to Oka, U.S. Pat. No. 4,740,536 to Chao, U.S. Pat. No. 4,772,643 to Ernst et al., Japanese Kokai Pat. No. Sho 47-33200, Japanese Kokai Pat. No. Sho 48-102157, Japanese Kokai Pat. No. Sho 50-123200, Japanese Kokai Pat. No. Sho 51-100128, and Japanese Kokai Pat. No. Sho 59-43016.
Alternatively, two-part coating systems can include, in lieu of amine as the "hardener" ingredient, an amide (see, e.g., U.S. Pat. No. 3,240,736 to Beckwith or Japanese Kokai Pat. No. Sho 56-161420), or a specified carboxylic acid (see, e.g., U.S. Pat. No. 3,256,226 to Fekete et al.), or an "amino"-containing ingredient (see, e.g., U.S. Pat. No. 4,598,108 to Hoefs), or an "amido"-containing ingredient (see, e.g., Japanese Kokai Pat. No. Sho 62-161803).
For a variety of reasons two-part systems of the type briefly mentioned above are inconvenient and thus undesirable. For example, because mixing of the mutually-reactive components typically quickly gives rise to crosslinking, whatever is not used becomes waste. Also from the standpoint of efficiency, it would be desirable to dispense with the "mixing" step. In particular, just prior to use, it would be desirable to dispense with that step which "mixes" or "combines" the epoxy-containing component with the hardener-containing component.
In U.S. Pat. No. 3,702,302 to Wilson, for example, there is disclosed a composition which consists of two, separate water-in-oil emulsion gels, wherein the two emulsion gels separately contain a respective one of two mutually-reactive chemical species. In particular, Wilson disclosed that one such water-in-oil emulsion gel has hydrogen peroxide in its water phase and the other water-in-oil emulsion gel has potassium sulfite in its water phase. Wilson neither discloses nor suggests, however, that such separate water-in-oil emulsion gels could be used to respectively contain an epoxy-containing component as well as a hardener-containing component to cause the epoxy moiety to "cure".
On the other hand, so-called "self-curable" compositions or formulations that include mutually-reactive chemical species such as epoxy-based "functional" polymers and amino-containing "hardener" polymers are well-known in the art. There has been great difficulty, however, in keeping such compositions from "curing" or crosslinking prematurely. Indeed, in connection with successful commercialization of such compositions, there has been a genuine concern for useful compositional pot life and stability.
One solution to the above-mentioned problem of premature reaction entails capping a reactive amino moiety or group of an amine-containing polymer with a ketone or aldehyde for the purpose of forming a so-called "ketimine", prior to mixing the amine-containing polymer with an epoxy-containing polymer. See, for example, U.S. Pat. No. 4,328,144 to Woo and U.S. Pat. No. 4,489,179 to Tortorello. After such a coating formulation is applied to a substrate, atmospheric moisture is said to cause the "ketimine" moiety to decompose thereby yielding reactive amino moieties which, in turn, coreact with the epoxy-containing moieties, for the purpose of effecting a desired "cure". There are, however, at least two major drawbacks to such a type of coating formulation. First, such a formulation is limited to non-aqueous systems; and, second, ketone, a solvent, is released into the immediate vicinity upon cure. It is well-known, however, that curable coating compositions that include solvent are generally undesirable. For example, many formerly-used well-known solvents have been deemed unsafe or otherwise environmentally unacceptable.
It would therefore be desirable, in view of the above, to reduce or--even better--totally eliminate use of such solvents in the production of durable, abrasion-resistant surface coatings that cure at room temperature. It would further be desirable that formulations providing surface coatings of this sort require no mixing at time of use yet remain stable for long periods of time.